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PubMed1993

Chemistry with confidence: should Clinical Chemistry require confidence intervals for analytical and other data?

Confidence intervals are not commonly provided with analytical or other data reported in Clinical Chemistry although P values are. However, confidence intervals provide an explicit demonstration of the direction and magnitude of uncertainty and are intuitively easy to grasp, unlike P values. It is therefore argued that the Journal should adopt a policy requiring the provision of confidence intervals. Such a policy would improve the statistical rigor of Journal reports.

Chemistry, Clinical↗
PubMed1985

Fluoride content of selected human food, pet food and related materials.

A survey was made of the fluoride content of selected human foods, some animal feeds, and related materials, with the purpose of a better characterization of products whose fluoride may contribute to the intake of fluoride by man as well as by some kinds of animals. Uptake of fluoride, especially from food with or without a foregoing food chain, was found to be more widely spread than has been documented previously. The major source of fluoride is represented by marine organisms, regardless of the ways by which man or animals are exposed to fluoride. As a consequence of the detailed analytical data given, recommendations would extend towards i) a more wide-spread analytical control of foods and feeds for fluoride, ii) an intensified assessment of fluoride bioavailabilities from foods and feeds, and iii) the consideration of such data in the evaluation of fluoride supplementations for optimized intakes, as recommended.

Animal Feed↗
PubMed2000

Dietary fat and breast cancer.

One of the most often studied associations in epidemiology is dietary fat and breast cancer risk. That migrants from low-risk countries increase their risk on immigrating to higher-risk countries suggests that some modifiable lifestyle or environmental factor is responsible for the development of breast cancer. Although early international correlational studies and experimental animals studies support dietary fat as a risk factor for breast cancer, more recent data from case-control studies and cohort studies have been equivocal, thus the analytical data do not support a strong positive association. The conflicting results from analytic studies may be due to methodologic issues associated with study design, dietary assessment tools, measurement error, improper statistical analyses, and a lack of heterogeneity in fat intake among the study population. Moreover, current dietary questionnaires may be inadequate in capturing true dietary intakes or capturing the risk with exposure during earlier periods of a woman's life. Although two large clinical trials investigating the fat/breast cancer relationships issue are underway, researchers are generally skeptical at their ability to detect an independent association between fat and breast cancer risk. Further epidemiologic studies using current methodology may not prove to be fruitful in generating definitive answers to shed light on this controversial issue. In addition, rather than concentrating on dietary fat, researchers should focus on diets that are not only low in saturated fat, but also high in fruit and vegetable consumption. Researchers should take advantage of advances in molecular and genetic technology for a different perspective in examining the issue. For example, markers of susceptibility to breast cancer that can detect women at higher risk for breast cancer may be helpful in clarifying the role of dietary fat. More comprehensive and multiple approaches to studying dietary factors and breast cancer are recommended.

Age Factors↗
PubMed1979

Classification of fungi by means of pyrolysis-gas chromatography-pattern recognition.

Repetitive samples of three strains of the mould Penicillium were subjected to pyrolysis-gas chromatography (Py-GC). From the chromatograms, 26 peak heights were used in a subsequent SIMCA pattern recognition analysis. This data analysis gives a marked improvement in the classification of the samples (100% correct, 85% unique) in comparison with the traditional analysis based on the average chromatogram of each class (92% correct, 45% unique). The data analytical method is described in detail using the Py-GC data as an illustration.

Analysis of Variance↗
PubMed1983

Use of anion gap for the quality control of electrolyte analyzers.

A simple model for the simulation of patient Na, CO2, Cl, and anion gap was formulated from patient electrolyte data. Analytical error, either random or systematic, was incorporated into the simulation of the electrolyte data and allowed study of the response of anion gap to error. Power functions, plots of probability of error detection vs. size of analytical error, were constructed and indicated a low probability of error detection when single patient specimens with abnormal anion gaps were reanalyzed. These power functions showed that pooling of the anion gap data by averaging consecutive anion gaps resulted in a high probability for detecting systematic error. We recommend, as a useful quality control procedure, averaging at least eight consecutive anion gaps and testing for a significant difference between the average and the established mean gap.

Acid-Base Equilibrium↗
PubMedDate not supplied

Improved quality data systems through the use of standard electronic data deliverables (EDDs) and environmental data assessment software.

One of the challenges facing professionals in the environmental arena today is the collection and assessment of large amounts of environmental analytical data. The assessment of the quality of that data is essential as multi-million dollar decisions for environmental site cleanups and/or long term monitoring efforts are made based on the analytical results. Also critical to environmental programs is the sharing and access of data across multiple data users. The ability to share data allows for better use of the limited resources available to clean up and monitor contaminated environmental sites. Standardization of electronic deliverables allows for collection of data from multiple data collectors into a single database for use by numerous data users and stakeholders on a project. This paper discusses the benefits of using a standard EDD deliverable format and use of environmental data assessment software tools to do project planning and data assessment throughout the duration of the environmental project.

Database Management Systems↗
PubMed1995

Standard reference materials and data quality assurance: the lesson from the analysis of trace elements.

The problem of having accurate and precise analytical data of the concentrations of trace elements and compounds in bioclinical studies is of fundamental importance. This can be conveniently faced if appropriate standard reference materials, with known concentrations of the analyte object of study, are available. This paper reviews the present situation of these standard materials in the field of trace element analysis in biological specimens. The most important requirements in the preparation and in the application of these materials are presented and discussed.

Evaluation Studies as Topic↗
PubMedDate not supplied

Organochlorine compounds in subtropical and tropical marine organisms: a meta-analysis.

A search of the published and unpublished literature was conducted for analytical data on organochlorine compounds in tissues of subtropical and tropical marine organisms. The search was limited to reports of analyte concentrations in whole body or muscle tissue that were minimally determined by chromatographic procedures. A total of 1564 sample analyses consisting of 4431 analyte determinations were obtained for hard and soft corals, sponges, benthic seagrasses and algae, gastropods, fish and shellfish, and 'market-basket' (processed seafood) samples. For comparative purposes, data that were reported on a wet- or fresh-weight basis were uniformly converted to a common dry-weight estimate by dividing the wet-weight values by five (i.e., 80% water, 20% dry-weight tissue). Due to the large variation in analytical procedures, target analytes, chromatographic interpretations, and reporting units, the data were pooled by organochlorine-compound class (i.e., chlorinated cyclodienes, chlorinated aliphatics, chlorinated phenols, and chlorinated terpenes, hexachlorocyclohexanes, and polychlorinated biphenyls). A meta-analysis of the resulting database yielded a mean analyte concentration of 1594 +/- 8768 ng g-1 (dry weight), a median concentration of 23 ng g-1 (dry weight), and a mean of 2.89 analytes per sample; the corresponding mean tissue burden is 4608 ng g-1 (dry weight), the equivalent of 922 ng g-1 on a wet-weight basis. It was also found that the chlorinated aliphatics (i.e., DDT and its metabolites) constituted 40.15% of the reported analyte determinations.

Animals↗
PubMedDate not supplied

Static and dynamic longitudinal structural analyses of cognitive changes in old age.

BACKGROUND: Among the main data-analytical advances of recent decades are Latent Growth Models (LGM) and Multilevel Models (MLM) for the analysis of longitudinal data. OBJECTIVE: We discuss the relative advantages and disadvantages of the two analytical methods and offer some practical guidelines concerning the choice between LGM and MLM based on (a). completeness and balance of the data, (b). theoretical functional form of change examined, (c). examination of the error structure, (d). theoretical relations among differential level effects and differential change effects, and (e). role of time-invariant covariates. METHODS: To discuss LGM and MLM, we provide illustrations from applications to the Berlin Aging Study (BASE) and the Swiss Interdisciplinary Longitudinal Study on the Oldest Old (SWILSO-O). RESULTS: As predicted by two-component theories of lifespan cognition, performance on a vocabulary test (indicator of broad crystallized intelligence) did not decline over time, while scores on a digit letter test (indicator of broad fluid intelligence) decreased over 6 years. Differential level effects were obtained on both variables, while average and differential change effects were obtained only for the digit letter test. In a second set of analyses, we tested the error-free effect that a broad fluid intelligence indicator exerted on the latent yearly change in a broad crystallized intelligence indicator, and vice versa. In both data sets we obtained strong evidence for a more reliable effect of the fluid indicator on the change in the crystallized indicator. This evidence provided support for the dedifferentiation hypothesis of cognitive abilities in very old age. CONCLUSIONS: New insights into cognitive aging phenomena can be gained with proper applications of LGM and MLM. We posit that the choice between LGM and MLM and their specification rests on theoretical and empirical motives to be defined a priori.

Aging↗
PubMed1990

Epidemiology of adenocarcinoma of the cervix.

There is general evidence that the incidence of adenocarcinoma of the cervix has been rising, particularly among younger women. The determinants of these trends, however, remain largely unknown. We have reviewed the epidemiology of adenocarcinoma of the cervix using descriptive data from cancer registration and clinical series and two main sources of analytical data: clinical studies comparing cervical adenocarcinoma (AC) and squamous carcinoma (SC) and formal case-control and cohort epidemiological studies. In both the United States and northern Europe there is evidence of the rising frequency of AC in absolute and relative terms as compared to SC. These trends are generally restricted to younger women: under-age-35 AC incidence approximately doubled from the early 1970s to the early 1980s. Available data, although scanty, consistently show that the frequency of cervical adenocarcinoma rises with the number of partners and with decreasing age at first intercourse, suggesting a potential role for sexually transmitted (viral) factors. In clinical series, nulliparity was reported more frequently in AC than in SC cases but an inconsistent association was found in three formal epidemiological studies. Similarities with the epidemiology of endometrial cancer are also suggested from the association with overweight, while a possible relation with hypertension and diabetes is based on clinical series only and hence more difficult to interpret. Thus, adenocarcinoma of the cervix appears to share epidemiological characteristics with both adenosquamous cancer of the cervix and adenocarcinoma of the endometrium, although uncertainties in classification and registration leave several questions unanswered.

Adenocarcinoma↗
PubMed2000

Research priorities for tobacco control in developing countries: a regional approach to a global consultative process.

OBJECTIVE: To develop regional tobacco control research agendas for developing countries through a consultative process. METHODS: Research for International Tobacco Control, located at the International Development Research Centre in Ottawa, Canada, convened three regional meetings for Latin America and the Caribbean, South and Southeast Asia, and Eastern, Central and Southern Africa. Participation by researchers, policymakers, and advocates from a wide range of disciplines ensured an accurate representation of regional issues. RESULTS: The four main recurring themes within each regional agenda were: (1) the lack of standardised and comparable data; (2) the absence of a network for communication of information, data, and best practices; (3) a lack of adequate capacity for tobacco control research, especially in non-health related areas such as economics and policy analysis; and (4) a need for concerted mobilisation of human and financial resources in order to implement a comprehensive research agenda, build partnerships, and stimulate comparative research and analysis. Specific research issues included the need for descriptive data with respect to the supply side of the tobacco equation, and analytical data related to tobacco use, production and marketing, and taxation. CONCLUSIONS: There was a uniform perception of tobacco as a multidisciplinary issue. All regional agendas included a balance of health, economic, agricultural, environmental, sociocultural, and international trade concerns. Research data are urgently required to provide a sound basis for the development of tobacco control policies and programmes. As tobacco control takes its rightful place on the global health agenda, it is vital that funding for tobacco control research be increased.

Developing Countries↗
PubMed1999

Mechanisms for the biological effectiveness of high-LET radiations.

Radiations of high linear energy transfer (LET) have long been known to have greater biological effectiveness per unit dose than those of low LET, for a wide variety of biological effects. However, values of relative biological effectiveness depend considerably on the biological system and in some instances the values are clearly below unity. The differences between high- and low-LET radiations may be due to many factors, almost all of which are related to radiation track structure in one way or another, and some can in principle lead to qualitative as well as quantitative differences between the radiations. Explanations for LET-dependent differences in effectiveness are discussed over a variety of levels from the multicellular and cellular scale down to the DNA scale, with illustrations from radiobiological data. Information from well-defined slow light ions provide particularly useful analytic data, but practical issues extend also to neutrons and fast heavy ions, which may compound high- and low-LET features. It is suggested that effectiveness of the radiation is determined predominantly by the complex clustered damage that it produces in DNA, but that for high-LET radiations long-term effects are in some instances limited by single-track-survival probabilities of the traversed cells.

Animals↗
PubMed1993

[The benefits of auditing clinical histories. Our experience over 5 years].

OBJECTIVE: To evaluate how our clinical records (CR) are filled in and to observe the impact of measures taken to correct faults found over a five-year follow-up period. DESIGN: Three descriptive studies (auditing methodologies) on representative samples of CR selected at random. Four quality indicators were fixed: internal communication (i.e. legibility and comprehensibility), external communication, manageability and the quality of the activity at attendances measured by the SOAP. The optimum standards (OS) were agreed by the team (technique of nominal group). SETTING: "Florida" Health Centre, Alicante. PATIENTS AND OTHERS PARTICIPANTS: Periodic team meetings to analyse results and agree activities. In 1986, N of CR = 367; in 1988, 370; and in 1990, 372. MAIN MEASUREMENTS AND RESULTS: During the follow-up period, the filling-in of all the variables, except the address, the test carried out and blood pressure, improved. But the following did not reach the OS: code, affiliation, origin, instruction, habits, allergies, working activity, socio-economic data, age and gender, family/personal background, test carried out, blood pressure and analytical data. The following all reached the OS: legibility, which went up from 88% to 96.5%, comprehensibility from 62 to 75.3%, external communication from 81 to 88.9%, manageability from 53 to 79.6% and SOAP from 62 to 82.5%. CONCLUSIONS: Auditing allows the level of the filling-in of the CR to be measured. Deficiencies which appear to be due to the design of the record itself can be detected. The efficacy of corrective measures to improve records can also be assessed.

Communication↗
PubMed2004

Deposition characteristics of methamphetamine and amphetamine in fingernail clippings and hair sections.

Fingernail clippings collected from 97 consenting females, who admitted amphetamines and/or opiates use and are currently under treatment, were quantitatively analyzed for the presence of methamphetamine and amphetamine. Sixty-two subjects were found positive for methamphetamine/amphetamine. Paired nail-hair specimens were collected from 6 of these subjects for a 12-week period and analyzed to determine the duration of detectability and deposition characteristics of amphetamines in fingernails; whether data derived from the analysis of nail clippings and hair sections are reflective of drug use patterns; and whether there is a relationship between the analytical data derived from the paired nail-hair specimens. Typical sample pre-treatment procedures and GC-MS protocols were evaluated to establish the validity of various analytical parameters and to ensure that the resulting data can be properly interpreted. Major findings include 1. Methamphetamine was found in the nails of 62 subjects collected in Week 0. The distribution of methamphetamine concentrations (ng/mg) in these nail samples are range, 0.46-61.50; mean, 9.96; and standard deviation: 13.33. The corresponding data for amphetamine are < 0.20-5.42, 0.93, and 1.01, respectively. 2. Sectional analyses of hair samples collected from 6 subjects in Week 0 show methamphetamine concentrations peak at different distances from the root. 3. The concentrations of methamphetamine and amphetamine in nail clippings are generally lower than the first 1.5-cm section of hair samples collected at the same time from the same individual. 4. Amphetamine/ methamphetamine concentration ratios in nail clippings and hair samples are comparable. 5. Methamphetamine concentration in the nail clippings collected at Weeks 0, 4, 8, and 12 decreases in a pattern similar to that exhibited by the first 1.5-cm sections of the hair samples collected at the same time.

Adult↗
PubMed1986

Modifications of lipid structure and their influence on mesomorphism in model membranes: the influence of hydrocarbon chains.

The influence of hydrocarbon chains on the temperature (TG-LC) of the gel to liquid-crystalline phase transition of model membranes has been investigated over an extensive variety of phosphatidylcholines (PC). The TG-LC is dependent upon the length of the hydrocarbon chains, on whether or not the chains are saturated or have been modified in some way, and on the position of any modification along the chain. For PC having two different acyl chains (heteroacid PC) in the sn-1 and sn-2 positions, the TG-LC is dependent on the chain position and on the inequivalence of chain penetration into the bilayer. Positional isomers of PC have different TG-LC. The first two double bonds introduced in each chain of a PC cause a much greater reduction in TG-LC and in the enthalpy change of the transition than does the subsequent introduction of additional double bonds. Dipolyunsaturated PC have uncooperative (broad) transitions that occur at low temperatures and have small enthalpy changes. While each PC has unique transitional characteristics, there are a number of patterns in the TG-LC which emerge on consideration of all the available data. One such pattern may be useful in predicting TG-LC from analytical data on the composition and positions of acyl chains of various lipids.

Chemical Phenomena↗
PubMed2000

[Application of computer base standards to pediatrics practice].

The computer base of medical standards to aid of pediatric diagnostic has been presented. The base include of anthropometric data (height and mass of body, some of circumferences, thickness of skinfolds etc.), analytical data (lipids) and also some of hemodynamic parameters (blood pressure). The programme allows graphical presentation of data as a percentile charts and also archives data. The basic of construction of computer base and examples of application has been presented.

Adolescent↗
PubMed2006

Measurement of the clinical and cost-effectiveness of non-invasive diagnostic testing strategies for deep vein thrombosis.

OBJECTIVES: To estimate the diagnostic accuracy of non-invasive tests for proximal deep vein thrombosis (DVT) and isolated calf DVT, in patients with clinically suspected DVT or high-risk asymptomatic patients, and identify factors associated with variation in diagnostic performance. Also to identify practical diagnostic algorithms for DVT, and estimate the diagnostic accuracy, clinical effectiveness and cost-effectiveness of each. DATA SOURCES: Electronic databases (to April 2004). A postal survey of hospitals in the UK. REVIEW METHODS: Selected studies were assessed against validated criteria. A postal survey of hospitals in the UK was undertaken to describe current practice and availability of tests, and identify additional diagnostic algorithms. Pooled estimates of sensitivity, specificity and likelihood ratios were obtained for each test using random effects meta-analysis. The effect of study-level covariates was explored using random effects metaregression. A decision-analytic model was used to combine estimates from the meta-analysis and estimate the diagnostic performance of each algorithm in a theoretical population of outpatients with suspected DVT. The net benefit of using each algorithm was estimated from a health service perspective, using cost--utility analysis, assuming thresholds of willingness to pay of pound 20,000 and pound 30,000 per quality-adjusted life-year (QALY). The model was analysed probabilistically and cost-effectiveness acceptability curves were generated to reflect uncertainty in estimated cost-effectiveness. RESULTS: Individual clinical features are of limited diagnostic value, with most likelihood ratios being close to 1. Wells clinical probability score stratifies proximal, but not distal, DVT into high-, intermediate- and low-risk categories. Unstructured clinical assessment by experienced clinicians may have similar performance to Wells score. In patients with clinically suspected DVT, D-dimer has 91% sensitivity and 55% specificity for DVT, although performance varies substantially between assays and populations. D-dimer specificity is dependent on pretest clinical probability, being higher in patients with a low clinical probability of DVT. Plethysmography and rheography techniques have modest sensitivity for proximal DVT, poor sensitivity for distal DVT, and modest specificity. Ultrasound has 94% sensitivity for proximal DVT, 64% sensitivity for distal DVT and 94% specificity. Computed tomography scanning has 95% sensitivity for all DVT (proximal and distal combined) and 97% specificity. Magnetic resonance imaging has 92% sensitivity for all DVT and 95% specificity. The diagnostic performance of all tests is worse in asymptomatic patients. The most cost-effective algorithm discharged patients with a low Wells score and negative D-dimer without further testing, and then used plethysmography alongside ultrasound, with venography in selected cases, to diagnose the remaining patients. However, the cost-effectiveness of this algorithm was dependent on assumptions of test independence being met and the ability to provide plethysmography at relatively low cost. Availability of plethysmography and venography is currently limited at most UK hospitals, so implementation would involve considerable reorganisation of services. Two algorithms were identified that offered high net benefit and would be feasible in most hospitals without substantial reorganisation of services. Both involved using a combination of Wells score, D-dimer and above-knee ultrasound. For thresholds of willingness to pay of pound 10,000 or pound 20,000 per QALY the optimal strategy involved discharging patients with a low or intermediate Wells score and negative D-dimer, ultrasound for those with a high score or positive D-dimer, and repeat scanning for those with positive D-dimer and a high Wells score, but negative initial scan. For thresholds of pound 30,000 or more a similar strategy, but involving repeat ultrasound for all those with a negative initial scan, was optimal. CONCLUSIONS: Diagnostic algorithms based on a combination of Wells score, D-dimer and ultrasound (with repeat if negative) are feasible at most UK hospitals and are among the most cost-effective. Use of repeat scanning depends on the threshold for willingness to pay for health gain. Further diagnostic testing for patients with a low Wells score and negative D-dimer is unlikely to represent a cost-effective use of resources. Recommendations for research include the evaluation of the costs and outcomes of using the optimal diagnostic algorithms in routine practice, the development and evaluation of algorithms appropriate for specific groups of patients with suspected DVT, such as intravenous drug abusers, pregnant patients and those with previous DVT, the evaluation of the role of plethysmography: interaction with other diagnostic tests, outcome of low-risk patients with negative plethysmography and measurement of the costs of providing plethysmography, and methodological research into the incorporation of meta-analytic data into decision-analytic modelling.

Adult↗
PubMed1990

Evaluation of criteria for the acceptance of bioanalytical data.

Results from bioanalytical analyses for registration of a new drug entity are used to define its pharmacokinetics and bioavailability/bioequivalence. Whilst analytical data may be derived from the application of a validated method, it is essential to apply mathematical criteria to its acceptance, in order that the analyst can be assured that the assay is performing within defined limits and to its validated specification. Parameters evaluated for acceptability are the batch calibration curve, the minimum quantifiable concentration and the quality control (QC) sample acceptability. Specifically, six QC samples per analytical batch are used, two samples at each of three concentrations. The rationale for the definition of these criteria is evaluated together with a consideration of their applications and limitations. The relevance and use of Shewhart and Cusum plots to monitor assay performance is illustrated.

Biological Availability↗